Japanese Utility Model Laid-Open No. Hei 3-54219 discloses an engine wherein an oil strainer includes a casing whose lower portion is formed in a funnel shape and is disposed within an oil pan in such a manner that an upper end portion of the casing is supported on a crank case side.
In the case of an oil strainer having a casing whose lower portion is formed in a funnel shape, a suction port formed in a lower end of the casing is narrow, so that an oil sucking flow velocity around the lower portion of the casing is relatively high and it is necessary to enhance the support strength of the casing so as to withstand the high flow. According to the related art, in order to meet this requirement, the inside diameter of an oil passage in which an upper portion of an oil strainer is fitted and supported is made large or the peripheral portion of the oil passage is thick-walled, or the oil strainer is supported by a stay which is mounted to the crank case. However, such structures result in an increase in the weight and the size of the engine. More particularly, in the case where the oil strainer is supported by a stay, not only an increase in the number of parts results, but also the layout is restricted for example by a partition wall disposed within the oil pan.